The present invention relates to a pattern-exposure photomask for use in manufacturing semiconductor devices or liquid crystal display devices, a method for producing the same, and a patterning method using the photomask, and also relates to a method for producing photomask pattern layout, and a method for producing mask-writing data.
In recent years, a large-scale integrated circuit (hereinafter, referred to as LSI) implemented with a semiconductor has been increasingly reduced in size. As a result, a feature error or dimensional error between a mask pattern and a produced pattern (e.g., a resist pattern formed by pattern transfer for a resist film) have been increasingly regarded as important in a lithography process, one of the LSI manufacturing processes.
Moreover, reduction in pattern dimension in the LSI has reached about the resolution limit defined by a wavelength of a light source (hereinafter, referred to as wavelength xcex), a numerical aperture of a projection optical system of an aligner (hereinafter, referred to as numerical aperture NA), and the like. As a result, a manufacturing margin associated with the yield in LSI manufacturing, e.g., a depth of focus, has also been significantly reduced.
In a conventional patterning method, a resist pattern having a prescribed feature is formed as follows: a light-shielding pattern of a prescribed feature, i.e., a mask pattern, is formed on a transparent substrate using a light-shielding film of a metal such as chromium. Then, a wafer having a resist film applied thereto is exposed to light using the transparent substrate having the mask pattern thereon as a mask, so that light intensity distribution having a profile similar to the mask pattern feature is projected to the resist film. Thereafter, the resist film is developed, whereby the resist pattern having the prescribed feature is produced.
A reduction projection aligner is generally used in such a patterning method as described above. For patterning, the reduction projection aligner conducts reduction projection exposure for a resist film of a photosensitive resin formed on a wafer, i.e., a substrate, by using a transparent substrate including a mask pattern with the dimension of a desired pattern magnified several times, i.e., by using a photomask.
FIG. 32(a) shows an example of a pattern whose minimum dimension is sufficiently larger than the resolution. FIG. 32(b) shows the simulation result of light intensity distribution projected to, e.g., a resist film upon forming the pattern of FIG. 32(a) using a conventional photomask.
More specifically, when the numerical aperture NA is 0.6 and the wavelength xcex is 0.193 xcexcm, the resolution is about 0.13 xcexcm. However, the minimum dimension of the pattern of FIG. 32(a) is about 0.39 xcexcm (about three times the resolution). The conventional photomask has a mask pattern having the dimension of the pattern of FIG. 32(a) magnified by the magnification M of the aligner (an inverse number of a reduction ratio). In this case,. as shown in FIG. 32(b), the implemented light intensity distribution has a profile similar to the feature of the pattern of FIG. 32(a), i.e., the mask pattern. Note that FIG. 32(b) shows the light intensity distribution using contour lines of the relative light intensity in a two-dimensional relative coordinate system (i.e., the light intensity calculated with the exposure light intensity being regarded as 1).
FIG. 33(a) shows an example of a pattern whose minimum dimension corresponds to about the resolution. FIG. 33(b) shows the simulation result of light intensity distribution projected to, e.g., a resist film upon forming the pattern of FIG. 33(a) using a conventional photomask.
More specifically, when the numerical aperture NA is 0.6 and the wavelength xcex is 0.193 xcexcm, the resolution is about 0.13 xcexcm. The minimum dimension of the pattern of FIG. 33(a) is also about 0.13 xcexcm. The conventional photomask has a mask pattern having the dimension of the pattern of FIG. 33(a) magnified by the magnification M. In this case, as shown in FIG. 33(b), the implemented light intensity distribution is significantly distorted from the profile similar to the feature of the pattern of FIG. 32(a), i.e., the mask pattern. Note that FIG. 33(b) also shows the light intensity distribution using contour lines of the relative light intensity in a two-dimensional relative coordinate system.
More specifically, as the minimum dimension of the pattern is reduced to about the resolution, the line width of the mask pattern on the photomask is also reduced. Therefore, the exposure light is likely to be diffracted when passing through the photomask. More specifically, as the line width of the mask pattern is reduced, the exposure light is likely to reach the backside of the mask pattern. As a result, the mask pattern cannot sufficiently shield the exposure light, making it extremely difficult to form a fine pattern.
In order to form a pattern having a dimension equal to or smaller than about the resolution, H. Y. Liu et al. proposes a patterning method (first conventional example) (Proc. SPIE, Vol. 3334, P.2 (1998)). In this method, a light-shielding pattern of a light-shielding film is formed on a transparent substrate as a mask pattern, as well as a phase shifter for inverting the light transmitted therethrough by 180 degrees in phase is provided in a light-transmitting region (a portion having no light-shielding pattern) of the transparent substrate. This method utilizes the fact that a pattern having a dimension equal to or smaller than about the resolution can be formed by the light-shielding film located between the light-transmitting region and the phase shifter.
Hereinafter, the patterning method according to the first conventional example will be described with reference to FIGS. 34(a) to (d).
FIG. 34(a) is a plan view of a first photomask used in the first conventional example, and FIG. 34(b) is a cross-sectional view taken along line Ixe2x80x94I of FIG. 34(a). As shown in FIGS. 34(a) and (b), a light-shielding film 11 is formed on a first transparent substrate 10 of the first photomask, and first and second openings 12 and 13 are formed in the light-shielding film 11 such that a light-shielding film region 11a having a width smaller than (resolutionxc3x97magnification M) is interposed therebetween. The first transparent substrate 10 is recessed under the second opening 13 so as to provide a phase difference of 180 degrees between the light transmitted through the first transparent substrate 10 through the first opening 12 and the light transmitted through the first transparent substrate 10 through the second opening 13. Thus, the portion of the first transparent substrate 10 corresponding to the first opening 12 serves as a normal light-transmitting region, whereas the portion of the first transparent substrate 10 corresponding to the second opening 13 serves as a phase shifter. Therefore, a pattern having a desired line width equal to or smaller than about the resolution can be formed by the light-shielding film region 11a located between the first and second openings 12 and 13.
FIG. 34(c) is a plan view of a second photomask used in the first conventional example. As shown in FIG. 34(c), a light-shielding pattern 21 of a light-shielding film is formed on a second transparent substrate 20 of the second photomask.
In the first conventional example, a desired pattern is formed by combination of a line pattern formed by the light-shielding film region 11a of the first photomask of FIG. 34(a) and a pattern formed by the light-shielding pattern 21 of the second photomask of FIG. 34(c).
More specifically, in the first conventional example, a substrate having a positive resist film applied thereto is exposed to light using the first photomask of FIG. 34(a). Then, the substrate is adjusted in position so that a desired pattern is formed by a latent image resulting from exposure using the first photomask and a latent image resulting from exposure using the second photomask of FIG. 34(c). After exposure is subsequently conducted using the second photomask, the resist film is developed, whereby a resist pattern is formed. Thus, excessive patterns (patterns other than the desired pattern) resulting from development after exposure with the first photomask only can be removed by exposure with the second photomask. This enables formation of a pattern having a line width equal to or smaller than about the resolution, i.e., a pattern that cannot be formed by exposure with the second photomask only.
FIG. 34(d) shows a resist pattern formed by the patterning method of the first conventional example, i.e., the patterning method using the first and second photomasks of FIGS. 34(a) and 34(c).
As shown in FIG. 34(d), the exposed substrate 30 has a resist pattern 31 formed thereon, and the resist pattern 31 has a line pattern 31a having a line width equal to or smaller than about the resolution.
In addition to the method of H. Y. Liu et al., Watanabe et al. proposes another patterning method (second conventional example) (Proc. of the 51st Annual Meeting of JSAP, P490). In this method, a pattern having a line width smaller than the wavelength xcex is formed without providing a light-shielding film between a light-transmitting region and a phase shifter. This method utilizes the effect that a pattern is formed by the boundary between a normal transparent substrate portion, i.e., a light-transmitting region, and a phase shifter.
Hereinafter, the patterning method according to the second conventional example will be described with reference to FIG. 35.
FIG. 35 is a plan view of a photomask used in the second conventional example. As shown in FIG. 35, a plurality of phase shifters 41 are periodically arranged on a transparent substrate 40 of the photomask.
In the second conventional example, the use of the phase shifters 41 enables formation of a pattern in which a plurality of line patterns each having a line width smaller than the wavelength xcex are arranged periodically.
However, in order to form a pattern having a line width equal to or smaller than about the resolution, the first conventional example must use a phase shift mask (first photomask) in which a light-shielding film region having a width of (resolutionxc3x97magnification M) or less is located between a phase shifter and a light-transmitting region both having a width of (resolutionxc3x97magnification M) or more. In other words, the pattern formed with the first photomask has a line width equal to or smaller than about the resolution only when specific conditions are satisfied. Therefore, an arbitrary pattern feature cannot be implemented with the first photomask only.
Accordingly, in order to form a pattern having a complicated feature like in the pattern layout of a normal LSI, exposure with a mask (second photomask) different from the phase shift mask is essential in the first conventional example. This results in increase in mask costs, or reduction in throughput as well as increase in manufacturing costs due to an increased number of lithography steps.
Moreover, a normal mask, i.e., a non-phase-shift mask, is used as the second photomask. Therefore, even if the exposures using the first and second photomasks are combined, the pattern formed by the second photomask has a dimension equal to or larger than about the resolution, whereby the patterns capable of being formed with a dimension equal to or smaller than about the resolution are limited. In other words, the first conventional example is used only when the phase shifter and the light-transmitting region can be located adjacent to each other under the aforementioned conditions, e.g., when only a gate pattern on an active region is formed.
In contrast, the second conventional example, i.e., the method in which a pattern is formed without providing a light-shielding film between a light-transmitting region and a phase shifter, can be used only when the patterns each having a line width smaller than the wavelength xcex are repeated. Therefore, a pattern having an arbitrary feature or an arbitrary dimension cannot be formed by this method alone.
Moreover, in the second conventional example, a portion where the phase changes abruptly must be provided at the boundary between the light-transmitting region of the transparent substrate and the phase shifter. However, by the conventional mask formation method in which a phase shifter is formed by wet etching the transparent substrate, the transparent substrate cannot be etched vertically at the boundary of the phase shifter. Moreover, when the transparent substrate is etched, a lateral region of the phase shifter in the transparent substrate is also subjected to etching, making it difficult to control the dimension of the phase shifter. As a result, it is extremely difficult to produce a mask capable of forming a fine pattern with high precision.
In the second conventional example, the dimension of the pattern formed by utilizing the phase shift effect is limited to about half the wavelength xcex. However, when a pattern having a larger dimension is formed with a mask pattern of a light-shielding film, the minimum possible dimension of the pattern corresponds to about the resolution. Accordingly, in the case where patterning is conducted using a single mask that simultaneously implements the phase shift effect and the light-shielding effect of the light-shielding film, a possible dimensional range of the pattern is discontinuous. This significantly reduces a process margin for forming a pattern of an arbitrary dimension with a single mask, and in some cases, makes it impossible to form a pattern with a single mask.
In view of the foregoing description, it is an object of the present invention to enable any pattern feature with any dimension including a dimension equal to or smaller than about the resolution to be formed by exposure using a single mask implementing a phase shift effect.
In order to achieve this object, the photomask according to the invention is a photomask including an isolated light-shielding pattern formed on a transparent substrate that is transparent to a light source. The light-shielding pattern is formed from a light-shielding film region formed from a light-shielding film, and a phase shift region having a phase difference with respect to a light-transmitting region of the transparent substrate which has no light-shielding pattern. A width of the phase shift region is set such that a light-shielding property of the phase shift region becomes at least about the same as that of the light-shielding film having the same width.
According to the photomask of the invention, the light-shielding pattern is formed from the light-shielding film region, and the phase shift region having a phase difference with respect to the light-transmitting region, and the width of the phase shift region is set such that the light-shielding property of the phase shift region becomes at least about the same as that of the light-shielding film having the same width. Therefore, the transmitted light reaching the backside of the light-shielding film region of the light-shielding pattern due to the diffraction phenomenon can be cancelled by the light transmitted through the phase shift region. Accordingly, even when a pattern having a dimension equal to or smaller than about the resolution is formed, light intensity distribution having a profile similar to the feature of the light-shielding pattern can be obtained. As a result, any pattern feature with any dimension including a dimension equal to or smaller than about the resolution can be formed by exposure using only the photomask of the invention implementing the phase shift effect.
In the photomask of the invention, a contour of the light-shielding film region is preferably the same as a feature of the light-shielding pattern, and the phase shift region is preferably provided inside the light-shielding film region.
Thus, the transmitted light reaching the backside of the periphery of the light-shielding pattern due to the diffraction phenomenon can be reliably cancelled by the light transmitted through the phase shift region.
In the photomask of the invention, the phase shift region is preferably provided at least at or inside a corner of the light-shielding pattern, or at or inside an end of the light-shielding pattern.
Thus, the transmitted light reaching the backside of the corner or end of the light-shielding pattern due to the diffraction phenomenon can be reliably cancelled by the light transmitted through the phase shift region.
Note that, in the specification, the term xe2x80x9ccornerxe2x80x9d means a portion having an angle larger than zero degree and smaller than 180 degrees when measured on the pattern.
In the photomask of the invention, provided that the phase shift region has a width Wm, it is preferable that Wmxc2x7(0.4xc3x97xcex/NA)xc3x97M (where xcex is a wavelength of the light source, NA is a numerical aperture of a reduction projection optical system of an aligner, and M is a magnification of the reduction projection optical system).
This ensures that that the light-shielding property of the phase shift region becomes at least about the same as that of the light-shielding film having the same width.
In the photomask of the invention, provided that the light-shielding pattern in which the phase shift region is provided has a width Lm, it is preferable that Lmxc2x7(0.8xc3x97xcex/NA)xc3x97M.
This enables a light-shielding effect of the light-shielding pattern to be improved by providing the phase shift region in the light-shielding pattern.
Provided that Lmxc2x7(0.8xc3x97xcex/NA)xc3x97M and the phase shift region has a width Wm, it is preferable that Wmxc2x7((0.8xc3x97xcex/NA)xc3x97M)xe2x88x92Lm and Wmxc2x7Lm.
This ensures improvement in the light-shielding effect of the light-shielding pattern.
Provided that Lmxc2x7(0.8xc3x97xcex/NA)xc3x97M and the phase shift region has a width Wm, it is preferable that 0.5xc3x97((((0.8xc3x97xcex/NA)xc3x97M)xe2x88x92Lm)/2)xc2x7Wmxc2x71.5xc3x97((((0.8xc3x97xcex/NA)xc3x97M)xe2x88x92Lm)/2) and Wmxc2x7Lm.
This enables significant improvement in the light-shielding effect of the light-shielding pattern.
In the photomask of the invention, the phase difference of the phase shift region with respect to the light-transmitting region is preferably (170+360xc3x97n) to (190+360xc3x97n) degrees (where n is an integer) with respect to a wavelength of the light source.
This ensures improvement in the light-shielding effect of the light-shielding pattern.
In the photomask of the invention, the phase difference of the phase shift region with respect to the light-transmitting region is preferably provided by etching at least one of a portion corresponding to the light-transmitting region and a portion corresponding to the phase-shift region in the transparent substrate.
Thus, the phase difference can be reliably provided between the phase shift region and the light-transmitting region.
In the photomask of the invention, the phase difference of the phase shift region with respect to the light-transmitting region is preferably provided by forming a phase shifter layer either on a portion other than the light-transmitting region or a portion other than the phase-shift region in the transparent substrate.
Thus, the phase difference can be reliably provided between the phase shift region and the light-transmitting region. The phase shifter layer may either be formed under or above the light-shielding film region.
A patterning method according to the invention is a patterning method using the photomask of the invention, and includes the steps of: forming a resist film on a substrate; conducting pattern exposure to the resist film using the photomask; and developing the resist film subjected to the pattern exposure so as to form a resist pattern.
According to the patterning method of the invention, the photomask of the invention is used. Therefore, even when a pattern having a dimension equal to or smaller than about the resolution is formed, the resultant light-shielding effect of the light-shielding pattern is about the same as that obtained when a pattern having a dimension equal to or larger than about the resolution is formed. As a result, any pattern feature with any dimension including a dimension equal to or smaller than about the resolution can be formed by exposure using only the photomask of the invention.
In the patterning method of the invention, the step of conducting pattern exposure preferably uses an oblique incidence illumination method.
This enables improvement in a process margin such as a depth of focus for a fine pattern.
In the patterning method of the invention, the resist film is preferably formed from a positive resist.
Thus, a fine resist pattern can be reliably formed by pattern exposure using the photomask of the invention. A negative resist may be used in order to form a fine resist-removed region like a hole pattern.
A method for producing a photomask according to the invention is a method for producing a photomask including an isolated light-shielding pattern formed on a transparent substrate that is transparent to a light source, the isolated light-shielding pattern being formed from a light-shielding film region and a phase shift region. The method includes the steps of: forming a light-shielding film on the transparent substrate; patterning the light-shielding film so as to form a contour of the light-shielding film region; and removing a portion of the light-shielding film located in the phase shift region so as to form an opening. The phase shift region has a phase difference with respect to a light-transmitting region of the transparent substrate, and a width of the phase shift region is set such that a light-shielding property of the phase shift region becomes at least about the same as that of the light-shielding film having the same width.
According to the photomask producing method of the invention, the patterning step for forming the contour of the light-shielding film region is conducted independently of the patterning step for forming the opening serving as the phase shift region. This enables accurate dimensional control of the contour of the light-shielding film region, i.e., the light-shielding pattern, and the phase shift region. Thus, the photomask of the invention can be reliably produced.
In the photomask producing method of the invention, the step of forming the opening preferably includes the step of etching, after forming the opening, a portion of the transparent substrate located under the opening such that a phase difference of (170+360xc3x97n) to (190+360xc3x97n) degrees (where n is an integer) with respect to a wavelength of the light source is provided between the portion and the light-transmitting region.
Thus, the phase shift region can be formed so as to reliably improve the light-shielding effect of the light-shielding pattern. In this case, the step of forming the opening is preferably conducted prior to the step of forming the contour of the light-shielding film region. This enables the transparent substrate to be etched using the light-shielding film with the opening as a mask. This eliminates the need to conduct formation of the opening and etching of the substrate successively by using a resist pattern as in the case where the opening is formed after formation of the contour of the light-shielding film region. Accordingly, production of the photomask of the invention is facilitated.
In the photomask producing method of the invention, the step of forming the contour of the light-shielding film region preferably includes the step of etching, after forming the contour of the light-shielding film region, a portion of the transparent substrate located outside the light-shielding film region such that a phase difference of (170+360xc3x97n) to (190+360xc3x97n) degrees (where n is an integer) with respect to a wavelength of the light source is provided between the portion and the phase shift region.
Thus, the phase shift region can be formed so as to reliably improve the light-shielding effect of the light-shielding pattern. Moreover, production of the photomask of the invention is facilitated as compared to the case where the phase difference is provided between the light-transmitting region and the phase shift region by etching the transparent substrate located under the opening having a small area.
In the photomask producing method of the invention, the step of forming the light-shielding film preferably includes the step of forming under the light-shielding film a phase shifter layer that provides phase inversion of (170+360xc3x97n) to (190+360xc3x97n) degrees (where n is an integer) with respect to a wavelength of the light source, and the step of forming the opening preferably includes the step of removing, after forming the opening, a portion of the phase shifter layer located under the opening.
Thus, the phase shift region can be formed so as to reliably improve the light-shielding effect of the light-shielding pattern. Moreover, management of the etching step is facilitated as compared to the case where the phase difference is provided between the light-transmitting region and the phase shift region by etching the transparent substrate. Thus, the phase error is reduced as well as the phase shifter layer with a vertical edge can be easily formed. In this case, the step of forming the opening is preferably conducted prior to the step of forming the contour of the light-shielding film region. This enables the phase shifter layer to be etched using the light-shielding film with the opening as a mask. This eliminates the need to conduct formation of the opening and etching of the shifter layer successively by using a resist pattern as in the case where the opening is formed after formation of the contour of the light-shielding film. Accordingly, production of the photomask of the invention is facilitated.
In the photomask producing method of the invention, the step of forming the light-shielding film preferably includes the step of forming under the light-shielding film a phase shifter layer that provides phase inversion of (170+360xc3x97n) to (190+360xc3x97n) degrees (where n is an integer) with respect to a wavelength of the light source, and the step of forming the contour of the light-shielding film region preferably includes the step of removing, after forming the contour of the light-shielding film region, a portion of the phase shifter layer located outside the light-shielding film region.
Thus, the phase shift region can be formed so as to reliably improve the light-shielding effect of the light-shielding pattern. Moreover, management of the etching step is facilitated as compared to the case where the phase difference is provided between the light-transmitting region and the phase shift region by etching the transparent substrate. Thus, the phase error is reduced as well as the phase shifter layer with a vertical edge can be easily formed. Moreover, production of the photomask of the invention is facilitated as compared to the case where the phase difference is provided between the light-transmitting region and the phase shift region by removing the phase shifter layer located under the opening having a small area. In this case, the step of forming the contour of the light-shielding film region is preferably conducted prior to the step of forming the opening. This enables the phase shifter layer to be etched using as a mask the light-shielding film having the contour of the light-shielding film but having no opening. This eliminates the need to conduct formation of the contour of the light-shielding film region and etching of the shifter layer successively by using a resist pattern as in the case where the contour of the light-shielding film region is formed after formation of the opening. Accordingly, production of the photomask of the invention is facilitated.
In the photomask producing method of the invention, the step of forming the opening is preferably conducted prior to the step of forming the contour of the light-shielding film region, the method preferably further includes, between the step of forming the opening and the step of forming the contour of the light-shielding film region, the step of forming on the transparent substrate a phase shifter layer that provides phase inversion of (170+360xc3x97n) to (190+360xc3x97n) degrees (where n is an integer) with respect to a wavelength of the light source, and the step of forming the contour of the light-shielding film region preferably includes the step of removing, before forming the contour of the light-shielding film region, a portion of the phase shifter layer located outside the light-shielding film region.
Thus, the phase shift region can be formed so as to reliably improve the light-shielding effect of the light-shielding pattern. Moreover, management of the etching step is facilitated as compared to the case where the phase difference is provided between the light-transmitting region and the phase shift region by etching the transparent substrate. Thus, the phase error is reduced as well as the phase shifter layer with a vertical edge can be easily formed. Moreover, if defects are produced in the step of patterning the phase shifter layer, it is possible to repair the defects by forming the phase shifter layer again. Therefore, the steps earlier than the step of forming the phase shifter layer need not be repeated, improving the throughput.
In the photomask producing method of the invention, the step of forming the contour of the light-shielding film region is preferably conducted prior to the step of forming the opening, the method preferably further includes, between the step of forming the contour of the light-shielding film region and the step of forming the opening, the step of forming on the transparent substrate a phase shifter layer that provides phase inversion of (170+360xc3x97n) to (190+360xc3x97n) degrees (where n is an integer) with respect to a wavelength of the light source, and the step of forming the opening preferably includes the step of removing, before forming the opening, a portion of the phase shifter layer located in the phase shift region.
Thus, the phase shift region can be formed so as to reliably improve the light-shielding effect of the light-shielding pattern. Moreover, management of the etching step is facilitated as compared to the case where the phase difference is provided between the light-transmitting region and the phase shift region by etching the transparent substrate. Thus, the phase error is reduced as well as the phase shifter layer with a vertical edge can be easily formed. Moreover, if defects are produced in the step of patterning the phase shifter layer, it is possible to repair the defects by forming the phase shifter layer again. Therefore, the steps earlier than the step of forming the phase shifter layer need not be repeated, improving the throughput.
In the photomask producing method of the invention, provided that the phase shift region has a width Wm, it is preferable that Wmxc2x7(0.4xc3x97xcex/NA)xc3x97M (where xcex is a wavelength of the light source, NA is a numerical aperture of a reduction projection optical system of an aligner, and M is a magnification of the reduction projection optical system).
This ensures that that the light-shielding property of the phase shift region becomes at least about the same as that of the light-shielding film having the same width.
In the photomask producing method of the invention, provided that the light-shielding pattern in which the phase shift region is provided has a width Lm, it is preferable that Lmxc2x7(0.8xc3x97xcex/NA)xc3x97M.
This enables a light-shielding effect of the light-shielding pattern to be improved by providing the phase shift region in the light-shielding pattern.
Provided that Lmxc2x7(0.8xc3x97xcex/NA)xc3x97M and the phase shift region has a width Wm, it is preferable that Wmxc2x7((0.8xc3x97xcex/NA)xc3x97M)xe2x88x92Lm and Wmxc2x7Lm.
This ensures improvement in the light-shielding effect of the light-shielding pattern.
Provided that Lmxc2x7(0.8xc3x97xcex/NA)xc3x97M and the phase shift region has a width Wm, it is preferable that 0.5xc3x97((((0.8xc3x97xcex/NA)xc3x97M)xe2x88x92Lm)/2)xc2x7Wxc2x71.5xc3x97((((0.8xc3x97xcex/NA)xc3x97M)xe2x88x92Lm)/2) and Wmxc2x7Lm.
This enables significant improvement in the light-shielding effect of the light-shielding pattern.
A method for producing pattern layout according to the invention is a method for producing pattern layout of a photomask including an isolated light-shielding pattern formed on a transparent substrate that is transparent to a light source, the isolated light-shielding pattern being formed from a light-shielding film region and a phase shift region. The method includes the steps of: extracting from the patter layout corresponding to the light-shielding pattern a line pattern having a width Lxc3x97M equal to or smaller than (0.8xc3x97xcex/NA)xc3x97M (where xcex is a wavelength of the light source, NA is a numerical aperture of a reduction projection optical system of an aligner, and M is a magnification of the reduction projection optical system); and providing inside the extracted line pattern a phase shift region having a width Wxc3x97M equal to or smaller than ((0.8xc3x97xcex/NA)xe2x88x92L)xc3x97M (where Wxc2x7L).
According to the pattern-layout producing method of the invention, a line pattern having a width Lxc3x97M equal to or smaller than (0.8xc3x97xcex/NA)xc3x97M is extracted from the pattern layout corresponding to the light-shielding pattern, and then a phase shift region having a width Wxc3x97M equal to or smaller than ((0.8xc3x97xcex/NA)xe2x88x92L)xc3x97M (where Wxc2x7L) is provided inside the extracted line pattern. Therefore, the phase shift region, i.e., mask enhancer, capable of enhancing the light-shielding effect can be provided in the portion of the light-shielding pattern having a degraded light-shielding effect, whereby the light intensity distribution can be projected onto the wafer with a less distorted profile with respect to the pattern layout. This enables production of the pattern layout of the photomask capable of forming any pattern feature with any dimension including a dimension equal to or smaller than about the resolution.
In the pattern layout producing method of the invention, it is preferable that 0.5xc3x97(((0.8xc3x97xcex/NA)xe2x88x92L)/2) Wxc2x71.5xc3x97(((0.8xc3x97xcex/NA)xe2x88x92L)/2) and Wxc2x7L.
This enables significant improvement in the light-shielding effect of the light-shielding pattern.
In the pattern layout producing method of the invention, the step of extracting the line pattern preferably includes the step of extracting a pattern corner or a pattern end from the pattern layout, and the step of providing the phase shift region preferably includes the step of providing at or inside the extracted pattern corner, or at or inside the extracted pattern end, the phase shift region with four sides of (0.5xc3x97xcex/NA)xc3x97M or less.
Thus, the transmitted light reaching the backside of the corner or end of the light-shielding pattern due to the diffraction phenomenon can be reliably cancelled by the light transmitted through the phase shift region.
A method for producing mask-writing data according to the invention is a method for producing mask-writing data of a photomask including an isolated light-shielding pattern formed on a transparent substrate that is transparent to a light source, the isolated light-shielding pattern being formed from a light-shielding film region and a phase shift region having a phase difference with respect to a light-transmitting region of the transparent substrate. The method includes the step of: extracting from pattern layout corresponding to the light-shielding pattern a line pattern having a width Lxc3x97M equal to or smaller than (0.8xc3x97xcex/NA)xc3x97M) (where xcex is a wavelength of the light source, NA is a numerical aperture of a reduction projection optical system of an aligner, and M is a magnification of the reduction projection optical system), and providing inside the extracted line pattern the phase shift region having a width Wxc3x97M equal to or smaller than ((0.8xc3x97xcex/NA)xe2x88x92L)xc3x97M (where Wxc2x7L) so as to maximize a light-shielding effect of the light-shielding pattern, and thereafter, adjusting a dimension of the phase shift region based on a result of test exposure or exposure simulation.
According to the mask-writing data producing method of the invention, the dimension of the phase shift region is adjusted based on the result of test exposure or exposure simulation after the phase shift region is provided so as to maximize the light-shielding effect of the light-shielding pattern. Therefore, the dimension of the phase shift region can be adjusted so that the dimension of the pattern resulting from exposure with the photomask becomes equal to the design value. Accordingly, mask-writing data capable of preventing withdrawal of the pattern and the like can be produced, whereby a fine pattern can be accurately formed by exposure with the photomask formed according to the mask-writing data.
In the mask-writing data producing method of the invention, the step of adjusting the dimension of the phase shift region preferably includes the step of reducing a width of the phase shift region corresponding to a portion having a pattern width larger than a design value as a result of exposure with the photomask, and increasing a width of the phase shift region corresponding to a portion having a pattern width smaller than the design value as a result of exposure with the photomask.
This ensures that the pattern resulting from exposure with the photomask has a dimension equal to the design value.